The present invention relates generally to microturbine power generating systems. More specifically, the present invention relates to modular, distributed power generating units.
The United States Electric Power Research Institute (EPRI) which is the uniform research facility for domestic electric utilities, predicts that up to 40% of all new generation could be provided by distributed generators by the year 2006. In many parts of the world, the lack of electric infrastructure (transmission and distribution lines) will greatly expedite the commercialization of distributed generation technologies since central plants not only cost more per kilowatt, but also must have expensive infrastructure installed to deliver the product to the consumer.
Small, multi-fuel, modular distributed microturbine generation units could help alleviate current afternoon "brownouts" and "blackouts" prevalent in many parts of the world. A simple, single moving part concept would allow for low technical skill maintenance and low overall cost would allow for wide spread purchase in those parts of the world where capital is sparse. In addition, given the United States emphasis on electric deregulation and the world trend in this direction, consumers of electricity would have not only the right to choose the correct method of electric service but also a new cost effective choice from which to chose. U.S. Pat. No. 4,754,607, which is assigned to the assignee of the present invention, discloses a microturbine power generating system suitable for cogeneration applications.
Yet to make these units commercially attractive to consumers, improvements are needed in areas such as increasing fuel-efficiency, reducing size and weight, and lowering thermal signature, noise, maintenance and cost penalties. For example, the units generate turbine exhaust streams that are very hot and, therefore, have high thermal signatures. Temperature of the exhaust stream is highest when a unit is operating at part-load. Before leaving the unit, heat from the exhaust stream is recuperated in a recuperator. However, if the temperature becomes too high, the recuperator can be damaged. Therefore, the turbine firing temperature is lowered during part-load operation to avoid damaging the recuperator. Consequently, efficiency of the unit is reduced.
There is a need to reduce the temperature of the turbine exhaust stream, without significantly lowering efficiency during part-load operation.